May 2013

May 27, 2013

In
the latest issue of JCB, Hartman et
al. reveal that dietary cholesterol stimulates follicle stem cell proliferation
to promote the production of Drosophila
eggs. Starving flies cease egg production, in part by sequestering Hedgehog
protein away from follicle stem cells in order to limit their proliferation. As
described in this week’s In Focus, however, cholesterol activates a pathway
that releases Hedgehog to initiate stem cell proliferation and rapidly restore
egg production.

Barriga
et al. show that the hypoxia inducible factor Hif-1α, which promotes the
epithelial-to-mesenchymal transition and migration of metastasizing cancer
cells, has a similar function during normal embryonic development. As explained
here, the researchers show that Hif-1α stimulates the collective migration of
neural crest cells by promoting expression of the chemokine receptor Cxcr4 and
the transcription factor Twist.

Ferreira
et al. describe how the Aurora B kinase and the microtubule end-binding protein
EB3 coordinate cytokinesis and daughter cell adhesion at the end of mitosis. A gradient
of Aurora B activity emanates from the spindle midzone, which allows
phosphorylated EB3 to stabilize midbody microtubules and promote cytokinesis,
while, at the cell cortex, unphosphorylated EB3 restricts microtubule growth to
promote the attachment of daughter cells to the underlying substrate. More
here.

Elsewhere,
Peters et al. reveal that low intracellular pH prompts starving yeast cells to
package their proteasomes into storage granules (summary here) and Kröger et al. describe how keratin intermediate filaments
promote intercellular adhesion by inhibiting the kinase PKC-α. You can learn
more about this latter story in this month’s biobytes podcast, where you can
also hear Mary Rose Bufalino discuss her recent study of how different fly stem
cell populations asymmetrically segregate damaged proteins, either retaining or
passing on the damage depending on the lifespan of their progeny. You can
listen below or subscribe in iTunes.

Finally for today, the JCB's Editor-In-Chief, Tom Misteli, explains a new initiative that hopes to reduce the importance of journal Impact Factors in determining the quality of a scientist's research. You can find his editorial, and all of the papers in the latest
issue by clicking here for the table of contents.

May 13, 2013

Kleiblova et al. identify mutations in the
phosphatase Wip1 that enable cancer cells to foil the tumor suppressor p53. As explained in this week's In Focus, the
mutations generate truncated versions of Wip1 that are more stable than the
wild-type protein, and are therefore better able to inactivate p53 and permit
cells to override the DNA damage checkpoint.

Snow
et al. reveal that Progerin, a mutant form of lamin A expressed in
Hutchinson-Gilford Progeria syndrome, disrupts the import of large protein
cargoes into the nucleus by lowering the levels of nuclear RanGTPase. More here.

Civelekoglu-Scholey et al. model the dynamics of metaphase chromosomes in Ptk1 cells. As explained here, Ptk1 cells represent in unusual case in which chromosomes at the edge of
the metaphase plate are immobile, whereas the ones in the central region
oscillate. Civelekoglu-Scholey et al. reveal that these different behaviors are due to regional differences in the strength of the polar ejection forces that push chromosomes toward the cell equator.

And Graziano
et al. report a new mechanism for controlling actin nucleation, identifying a
budding yeast protein, Bil1, that activates the nucleation promoting factor
Bud6, which, in turn, stimulates the formin Bnr1 to initiate actin cable
assembly. As described in this summary, this is an unusual way of regulating actin assembly, as nucleation tends to be initiated by proteins working in pairs, rather than in groups of three.

And, finally for today, this
month’sbiosights video podcast features Roberta Martinelli and Christopher Carman, who discuss their recent paper describing how a loss of tension
inside endothelial cells induces the formation of ventral membrane protrusions
that close the holes left by transmigrating leukocytes. You can watch it here or subscribe in iTunes and, if you'd like to discuss Martinelli et al.'s findings with your lab, you can
download a “Journal Club Pack” – including a pdf of the paper and a PowerPoint
file of their figures – by clicking here.

That's all for today, but you can find the full table of contents for today's new issue by clicking here.

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